A wireless LAN (Local Area Network) in a 5 GHz band shares a frequency band with a radar system such as a weather radar. It is mandatory to mount a DFS (Dynamic Frequency Selection) function in a wireless LAN system as a sharing condition.
In the DFS function, it is necessary to check whether or not a radar wave is detected before starting communications on each frequency channel (for example, after the system is powered on or after channel switching) for one minute, and communications cannot be performed on the frequency channel during this check. Further, when a radar wave is detected during communications, it is necessary to stop the use of the frequency channel which has been used for the communications till then, and switch to another frequency channel.
In the above-mentioned case, even if the switching to another frequency channel is carried out in order to continue the communications which have been performed till then, the one-minute checking of radar wave detection must be performed also on the frequency channel which is the switching destination, and the communications are suspended during the check. When a radar wave is detected also for the frequency channel which is the switching destination, it is necessary to further switch to another frequency channel, and therefore there is a possibility that the suspension of the communications becomes still longer. Various technologies have been proposed in order to solve this problem associated with convenience.
For example, in a device described in patent reference 1, a wireless LAN access point has a plurality of wireless interfaces, and, when communications in one wireless interface are stopped because of detection of a radar wave, or the like, communications are provided via another wireless interface.
Further, in a wireless communication device described in patent reference 2, a wireless LAN access point is provided with a plurality of wireless units each having a function of detecting a radar wave and a data communication function, and, when performing channel switching, one wireless unit temporarily performs a data communication operation and another wireless unit operates in parallel with the wireless unit so as to detect a radar wave.